About the Author
Geoff Hill, inventor of the Tetrahedral Test Chamber (TTC) and CTO at Hill Acoustics, has been working in the loudspeaker and audio industry for more than 40 years. He is Chair of the AES SC-04-03 Working Group on loudspeaker modeling and measurement and a member on the IEC Working Group TC 100/TA 20/PT 60268-22. He is also the author of Loudspeaker Modelling: A Practical Introduction. Geoff welcomes your comments and can be contacted via email geoff@hillacoustics.com.
In Part 2 of this article series focusing on loudspeaker measurement standards, I discuss how these new standards apply to measurements of sound in 3D space and in production environments, measurement of SPL using voltage sensitivity, and the measurements of microspeakers.
Measurement of Sound in 3D Space
In IEC 60268-21:2018 there is a totally new section that addresses, in my view, one of the biggest limitations to practical loudspeaker measurements-namely the anechoic chamber. These new standards address the measurement environments and probably the most significant change is the move away from the anechoic chamber and toward defined acoustical environment and the target environment-as in a car's cabin. And importantly, for the first time the standards specify the positioning of both the loudspeaker and microphone, in the X, Y, and Z planes-using spherical coordinates so at last we know what and where we are measuring.
Measurements can now be made in a 3D space in both conventional anechoic and non-anechoic rooms (Figure 6). Using holographic wave expansion we can predict the far-field performance from the near-field response(s), allowing measurement of the radiated power over a specified angle or coverage. This subject is covered in more detail by AES56 (the AES standard on acoustics-Sound source modeling-Loudspeaker polar radiation measurements).
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Diese Geschichte stammt aus der October 2022-Ausgabe von audioXpress.
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